An aerial photo of the Hong Kong skyline taken on Dec. 19e 2018. Dale De La Rey / AFP via Images
It is clear from the increase in cases in Europe and the United States that we cannot make the mistake of relying solely on vaccines for the protection of the population. We must fight against Covid fatigue and maintain the effectiveness of public health protocols consisting of testing, tracing and isolating. Here, I describe a new study from Hong Kong that further validates this approach by demonstrating how effective strict quarantine policies are in controlling the transmission of Covid without the need for city-wide lockdowns. Only 6 of 4,198 study participants tested positive for anti-SARS-CoV-2 antibodies after three waves of Covid that occurred before the vaccination rollout in Hong Kong.
Despite a relatively slow vaccine uptake, Hong Kong is one of the few placess to have successfully controlled Covid cases at each stage of the current pandemic. Daily cases have never exceeded 180 per day and the average number of daily cases as a result of the Delta variant that has ravaged so many other places is between two and eight cases. It is especially impressive in a densely populated city like Hong Kong. These results are due to rigorous contact tracing, targeted testing blitzes, and strict checks and quarantines.
The authors of the Hong Kong study set out to find out if there were any asymptomatic or unidentified cases that were not included in this low daily case count and conceived a study to assess the prevalence of unidentified SARS-CoV-2 infection. A prospective cross-sectional study was conducted in Hong Kong after each major wave of the Covid-19 pandemic (April 21 to July 7, 2020; September 29 to November 23, 2020; and from 1January 5 to April 18, 2021). A total of 4,198 adults who had not been diagnosed with Covid-19 were recruited during each period, and their socio-demographic information, symptoms, travel, contacts, quarantine and history of Covid-19 testing were collected. IgG antibodies to SARS-CoV-2 were detected by a spike protein-based enzyme immunoassay (S1 / S2), followed by confirmation with a commercial electrochemiluminescence immunoassay based on the domain of spike protein receptor binding. All participants were tested for IgG antibodies to SARS-CoV-2 using a spike protein-based enzyme immunoassay (S1 / S2), followed by confirmation with a test. Commercial electrochemiluminescence immunoassay based on spike protein receptor binding domain.
Overall, 6 participants were confirmed positive for antibodiesSARS-CoV-2. Two participants with positive results were from the first recruitment, 1 from the second recruitment and 3 from the third recruitment which corresponded to positivity rates of 0.22% (2 in 903), 0.10% (1 in 1046) and 0, 13% (3 of 2,249). The researchers used these percentages and applied a weighted adjustment for the sex and age distribution of the general adult population in Hong Kong to estimate the number of unidentified SARS-CoV-2 infections.
The adjusted prevalence of unidentified infections was found to be 0.15%, with less than 1.9 unidentified infections for each recorded case. The results suggest that strict isolation and quarantine policies, even without a full city lockdown, are very successful in minimizing the transmission of SARS-CoV.
Yourrigorous tracing and isolation is a very effective Covid control policy that the United States and many other countries have never fully embraced. As we continue to fight vaccine reluctance and waning immunity in those who are vaccinated, our arsenal must include more than just medical defenses. The best strategy will combine the powers of medical and public health defenses to include vaccination with boosters as directed, antiviral drugs, testing, tracing, quarantine, ventilation, and masking as appropriate.